While navigation devices as described above were initially limited to those of the type integrally fixed to the vehicle, recently, those of the portable type easy to carry around have been proposed. Also proposed are navigation devices of the detachable type enabling only the portion provided with the navigation function to be detached, for further improvement of the usability. A navigation device of the detachable type includes a body (or, base unit) that is integrated with an audio device or other component installed in front of a driver's seat in the vehicle, and a portion (or, front panel unit) configured to be attachable to and detachable from the body. The detachable portion has the navigation function, and thus, even when detached from the body, it can be used outside the vehicle in which the body has been installed or taken home for use in destination search or the like.
On the other hand, antitheft measures are essential for vehicles including automobiles. As a way of enhancing the antitheft function, there has been proposed a configuration in which when a dedicated ID card (see Japanese Patent Application Laid-Open No. 2004-114890) or a driver's license card (see Japanese Patent Application Laid-Open No. 2006-273301) is inserted into a prescribed card receiver, the antitheft lock function is released to enable the operation of the ignition key, so that the engine can be started.